DEPARTMENT OF GENETICS. 149 



and the results have been presented in two papers: 'The influence of 

 alcohol on the fertility of white rats" and ''Alcohol and the growth of 

 white rats" (to appear in Genetics). Dr. ^^lacDowell reports on his 

 results as follows : 



"The data on fertihty include: (1) the numbers of rats per litter; (2) the 

 numbers of Utters produced by the tests and controls in the same time. The 

 summaries are based on 177 pairs of rats, which produced in all 1,755 off- 

 spring. In all the experiments dealing with alcohoUsm, this is probably the 

 first time that the fertility of treated animals has been tested by comparisons 

 with full brother and sister controls. The first series of experiments, those 

 with the light dosage, shows an average reduction of 11.5 per cent in the 

 size of the litters produced by the treated females by treated males, as com- 

 pared with the average litter-size of the controls; in the second series of 

 experiments, those given the maximum dosage, the corresponding difference 

 is about the same, namely, a reduction of 10 per cent in the size of the litters 

 produced by the treated parents. The treated children of the treated rats 

 produced fitters that were 10.3 per cent smaller than the corresponding con- 

 trols. So it appears that treating the parents as well as the rats themselves 

 does not intensify the reduction in the size of the litters produced. The 

 untreated children of treated parents produced litters that were 11.2 per cent 

 smaller than the controls, and the untreated grandchildren from untreated 

 parents and treated grandparents produced litters that averaged 13.1 per 

 cent smaller than the controls. Although these differences in each genera- 

 tion by itself are not based on large enough numbers to make them statis- 

 tically significant, when the litters in all the generations are taken together, 

 the probable error is reduced so that the difference is fully significant (3.6 

 times its probable error). 



"Given equal time, the treated rats produced 0.72 litter per pair, while 

 the controls produced 2.07 fitters per pair. This is a reduction of 64.86 per 

 cent ±3.37 in the number of litters, and, as it is 19.2 times its probable error, 

 it is significant beyond all question. The first fitters produced by the treated 

 rats were slower in appearing than the controls, although the treated and 

 control pairs were mated at the same age. So, besides giving fewer litters, 

 the treated pairs were slower in producing the litters that were born. Turn- 

 ing to the numbers of litters produced in the later generations, the treated 

 rats from treated parents also produced fewer litters than the controls, but 

 instead of a greater reduction than in the previous generation, this second 

 treated generation produced relatively more litters. The reduction was 

 35.45 per cent ± 6.91 of the controls. Coming to the rats not directly treated, 

 untreated rats from treated parents gave 33.30 per cent ±8.20 more fitters 

 than their controls, and the untreated rats from untreated parents and treated 

 grandparents produced 55.60 per cent±8.40 viore litters than the controls in 

 the same generation. All of these differences are fully significant. 



"From the above statements, it is clear that the factors that condition 

 the size of fitters are not identical with those for the numbers of fitters. 

 The effect of alcohol upon the size of litters in all generations studied is 

 relatively constant, whether the parents themselves were treated or only the 

 grandparents, or great-grandparents; but the number of litters is strongly 

 reduced when the parents themselves are treated, though when the alcohol 

 is more remote the reduction vanishes; the later descendants of the treated 

 rats produce more litters than the controls. To explain the reduction in 

 the number of fitters in the presence of alcohol along purely physiological 

 fines would be a simple matter, but a genetic explanation is required when it 



